Although there are no rigid rules for oil painting, it is good to know the different methods used by painters, so you can experiment with different ways, colors and compositions. If you are painting a simple theme, such as a landscape with a large area of sky, there is usually no need for underpainting or a background drawing, except perhaps a line to indicate the horizon. For more complex topics, it is recommended to prepare a drawing that will set the composition, the main elements, and determine the balance of shapes and colors. With good planning at the beginning, later you get more freedom and spontaneity.
The background drawing can be done with a pencil or charcoal. To prevent the charcoal particles from mixing and getting dirty, wipe the surface with a cloth before painting. even if you sweep the surface, the outlines of the drawing will remain.
Underpainting is a type of subject to drawing that is performed with a brush. It can be monochrome or colored. In both cases the dye is diluted with turpentine. The focus should be on the main surfaces, light surfaces and those in the shade, and avoid too bright colors.
Today’s painters usually use acrylic paints for underpainting because they dry faster than very dilute oil paints.One of the old rules is to paint “thick over thin”, which means that in the initial phase of painting you should use a fairly diluted paint (diluted only with turpentine) which becomes denser as the work progresses. diluted, thin paint applied over a thick, thick layer containing more oil, may crack as the bottom layer shrinks on drying.
But not all pictures are painted that way. Many are completed at once, with or without minimal underlying drawings and underpainting. This way of painting is called “alla prima”, and it is very free and spontaneous. When painting “alla prima”, thick spreads are used, and each color is applied as it will look in the end. The colors are mixed on the palette, but also by applying one over the other. This form of “alla prima” painting is called the “wet on wet” method, and it has been used extensively by the Impressionists, especially Claude Monet in outdoor painting. If you haven’t tried oil painting yet, this method is a good start because it gives you an “instant feel” for this technique.